de Havilland Mosquito

20 Jan 13 - Fuselage to be rebuilt (probably).

DH Mosquito DH Mosquito DH Mosquito DH Mosquito DH Mosquito DH Mosquito  

The 4 photographs to the left were immediately prior to the ill-fated first flight, and to the 2 to the right after repair.

I originally intended to build a 1/6th scale model, but for the moment I am going to build a 1/9th scale model instead. This is mainly because I don't have the time at present to start such a major project.

1/9th Scale Model - Modified Mosquito FB VI (naval prototype for the mark TR33).

I was considering building the Mk TR33 which was a naval modified FB VI. This version was the a torpedo reconnaissance version and the first twin-engined aircraft used on Royal Navy ships. The production models featured folding wings (manual) and later optional RATO (Rocket Assisted Take Off) bottles. They carried the normal Mosquito cannons (but not machine guns), bombs, rockets and cameras, but additionally and externally slung 18" torpedo. The only feature I don't like on the TR33 is the ASH blister radar on the nose. I have avoided this feature by modelling the prototype TR33, which was a production FB VI variant modified by installation of fuselage side reinforcing and an arrester hook. Initially I won't be fitting the arrester hook, but intend to fit a fully functional hook later. This aircraft had a fairly unusual colour scheme for a Mosquito, comprising of an (Extra) Dark Sea Grey upper section over a Yellow underside.

N of launches / Time 3 6 mins

Flights & time reflects all configurations

  2 x AstroPower Leisure brushed 2 x Mega S5 brushed 2 x TBC brushless
Wingspan 71 in. 1.8 m        
Wing Area 735 in 47.4 dm        
Flying Weight 12 lb. 4 oz. 5.56 kg 12 lb. 10 oz. 5.73 kg    
Wing Loading 38.4 oz/ft 117.2 g/dm  39.6 oz/ft 120.8 g/dm    
Wing Cube Loading 17.0 - Racer (Ouch! - but probably near scale) 17.5 - Racer (Even worse but it's got more power)  
Motors 2 paralleled AstroPower Leisure (Australia) ND-10 wound for 12 - 14 cells. 2 x Mega S5 in series TBC
Gearboxes 4:1 built-in to the motor. None - direct drive None - direct drive
Propellers 2 x APC 12" x 8" 2 x APC 12" x 8" TBC
Motor Batteries 16 Sanyo RC-2400 cells. 20 Sanyo RC-2400 cells. TBC
Speed Controller 2 x Gordon Tarling Micro-Star 40 - 6 to 30 cells, 40A Gordon Tarling Micro-Star 40 - 6 to 30 cells, 40A TBC
Receiver / battery JR NER-649R - 9ch - S-PCM - 35MHz
with 4 cell RC-2000 pack (for ballast).
JR NER-649R - 9ch - S-PCM - 35MHz
with 4 cell 1300 mAh pack.
Spektrum 2.4 GHz TBC
Servos Ailerons 2 x Hitec HS-81MG 2 x Hitec HS-81MG TBC
Elevator Hitec HS-300BB Hitec HS-300BB TBC
Rudder Hitec HS-300BB Hitec HS-300BB TBC
Flaps 2 x Hitec HS-225MG 2 x Hitec HS-225MG TBC
Undercarriage Fleet FPS-15 micro & pneumatic retracts Fleet FPS-15 micro & pneumatic retracts TBC
Static motor parameters 5850 rpm @ 50A (25A each motor) after 30 seconds, and an estimated 64W/lb. 7000 rpm @ 35A after 30 seconds, and an estimated 64W/lb. Not yet tested
Flight performance The acceleration on the ground roll was quick and the model climbed away well. I have now completed a couple of short flights and the model behaves well. You can't afford to slow down too much or it tip stalls (found out at height). I have managed a single roll, which was very barrel shaped and more aileron deflection would be useful. Never successfully flown in this configuration. Not yet flown

20 Jan 13 - I have been looking at the wing (intact) & fuselage (in pieces) in the garage and think it would be fairly easy to get this Mosquito flying again.  This is mostly due to the potential increase in power and reduced weight possible with brushless motors and LiPo batteries.  I think a built-up tailplane, fin & rudder should help reduce the weight at the rear and simplify battery placement.

11 Sep 01 - Having attempted to take-off a number of times on grass, the model flipped over and broke it's back. As the model is already seriously overweight, I have decided to scrap it. Maybe I'll build another in the future...

11 Mar 01 - I have now completed the mounts from a piece of aluminium  'L' section 40mm x 10mm x 1.6mm thick. These are bolted to the nacelle side sheets to allow adjustment of right and down thrust and propeller fore and aft position.

25 Feb 01 - I have been having problems with the motor mounts failing whilst running on the ground. I have decided that they need replacing and will be making some aluminium mounts in the near future to cure the problem.

9 Dec 00 - I tested the Mega S5 motors today.. Despite only having 94% of the input power, the motors are turning about 20% faster, a total of 27% improvement in efficiency. I will in the longer term probably increase to 24 cells, but this require an ESC capable of 50A continuous. The motors & additional cells will have increased the aircraft weight by about 14 oz. (400g). However, I should be able to remove most of the ballast weight saving up to 12 oz. there. I'll weigh her again once I've completed the balancing.

25 Nov 00 - I have now finished the modifications to the Mosquito. The 2 Mega S5s (in series) are fitted and static power trails will commence shortly. These will be used to determine the optimum number of cells and propellers for this set-up. I have also completed moving the main undercarriage forwards by 1" (25mm). This should hopefully allow the model to roll to a stop without ending up on it's nose. This is also a more scale-like position, which is a nice advantage.

21 Oct 00 - I now have a pair of Mega S5s, which will fit the bill perfectly. These are normally run on between 10 and 14 cells (per motor), so I will be running them in series, initially on 24 cells. This means I have lost the ability to run one motor independently, but I doubt I would have used it in the air much anyway (if ever).

10 Aug 00 - I had a motor problem on the last outing, which I finally got around to investigating. One motor suddenly started to decelerate and eventually stopped. On dismantling, I discovered that the motor had obviously overheated and melted the back plate. This motor will require the commutator to be skimmed and a new backplate to be fitted. I am very obviously exceeding the maximum power that these motors can handle. On checking, they are rated at 300W and I am driving them at almost 400W (oops). I will have to find an alternate motor that will handle the necessary power. I would really like to get up to 500W each and will require a bigger motor, maybe a pair of Megas.

31 Jul 00 - I have now managed to get a couple of flights in on the Mosquito and it flies quite well. It is quite difficult to launch without it tipping on it's nose as the CofG is too close to the wheels. This is a fault of the kit design, but some extensive changes should improve the situation. I am going to attempt to move the undercarriage retracts 1" (25mm) forward, which should help immensely.

11 Jul 00 - I have now fitted APC 12" x 8" propellers to replace the damaged set. Whilst these may not give the same static thrust they are more efficient above 7000 rpm, which should be achieved in flight.

4 Jul 00 - I have adjusted the undercarriage to give it approximately 0.25" (6.5mm) more forward rake. I have also removed the small ballast weight, which shifts the CofG back by 0.1" (2.5mm). Whilst fairly small changes, I hope it will help keep the tail down.

30 Jun 00 - I attempted another test flight today, but it was unsuccessful. This time, however, it was due to the model tipping onto it's nose and shredding the tip of one propeller. As I had just used the spare set during the rebuild, a been unable to get replacements by then, it curtailed any further attempts.

28 Jun 00 - The repairs are now completed, and I've even painted the canopy & spinners that I didn't before. I think I made a mistake when working out the CofG before and had the undercarriage down. The weight of the legs and wheels is not small, and they move quite a long way (especially the wheels). To help with the CofG, I moved one battery pack forward by 3" (90 mm), uprated the RX pack to RC-2000 cells. Despite this, I still had to add 12 oz. (350g) of lead under the batteries to get the CofG right. This weight gain is not exactly welcome, but I'll make the most of it.

15 Jun 00 - The wing is now rejoined, and will have sub-spars fitted to reinforce the weakened centre section.

2 Jun 00 - Construction was completed a couple of days ago, and the test flight was made today. The model took off well, but was very unstable in pitch. I was trying to make a circuit to land and decided to retract the undercarriage (big mistake). Part way around the circuit the model nose up a little more and flicked into a spin. I could not recover the model and it hit the ground hard from about a 100 ft spin. I have decided the model is repairable, but will take some work. The CofG was slightly aft of the stated position, but not by much. This was definitely the worst kit I've ever had with several major inconsistencies in the instructions. I was consider that it was a major mistake by the company not to build washout into the outer panels.

5 May 00 - I have completed all the airframe construction and saved about 225g (8oz.) from the original weight. The aircraft is also fully covered in an combination of Solarfilm, Profilm (Oracover) and Easycoat. I have started to spray the underside with the Yellow paint and will be mixing a suitable colour for the upper surfaces shortly.

15 Apr 00 - I have now have both motors, the Mustang completed, and construction continues slowly. I have built the nacelle / engine mount structure, fitted the retract units, cut out all the wing control surfaces (including the flaps I've added). I have almost completed the fitting of the nacelle panelling. I have decided to model the prototype, a modified FB VI, for the TR33 Sea Mosquito. I am working out how to best fit an arrester hook to the aft fuselage for carrier deck competitions. I have so far removed about 100g (3.5 oz.) from the original construction.

I am still evaluating different options for the power train. Cobalt (brushed) motors or brushless seem the best option. These will run through suitable gearboxes to allow the use of a scale diameter propeller. The ESCs to be used will depend on the motors chosen to power the model. I may use my Extra Slim as a flying test bed to prove the power train.

As it is unlikely that I will be able to operated the motors in series, due to the number of cells, I intend to use a gyro on the rudder. In the event of a motor failure the gyro will hopefully stop the yaw developing and prevent the model entering into a spin.

I have now started construction of the model and will be attempting to lighten the design (originally intended for slimer power) as I go. I have finished adding the foam deckings to the fuselage, and these have had the middle removed to lighten them. I had to make a new section of decking for the lower front piece as the kit manufacture had made the piece incorrectly. I replaced the heavy ply formers in the canopy frame and fixings with liteply. I have now bonded the outer wing panels to the inner panels and fitted the leading & trailing edges and aileron cut-out stiffeners. I now have the retracts for the model, but I am still awaiting 1 motor. I will be continuing construction when I finish the Mustang.

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